Please note: Microwave ovens vary both in physical appearance and operation. Therefore, always reading the manual for the particular microwave you are using due to different protocols for different models etc.
For example, domestic, laboratory and commercial microwave ovens can use different power control strategies (variable versus on/off) and operation (turntable versus flatbed).
(a) metal objects (such as aluminium tape) are NOT put in the microwave oven
(b) no sealed containers (such as bottles with screw lid) are heated in microwave oven
The following links provide information and guidance on the safe use of microwave ovens.